1. Field of the Invention
The present invention relates to an image sensor.
2. Description of the Related Art
Life science-related objects, such as drugs, foods, and living bodies, absorb light of an infrared wavelength range of approximately 1 μm to 3 μm. As the technology in the life science field is developed, the demand for infrared image sensors also increases in the life science field. The infrared image sensors are usually Cooled to, for example, liquid-nitrogen temperature during operation. With improvements in semiconductor technology, infrared image sensors have sufficiently high image quality, even if the infrared image sensors are cooled by using thermoelectric device such as a Peltier device. In addition, the infrared image sensors have become smaller in size. For example, “Two-Dimensional Near Infrared Sensor with Low Noise and Wide Wavelength Range”, SEI TECHNICAL REVIEW, NUMBER 76, pp. 98-101, APRIL (2013) by Yasuhiro IGUCHI et al. discloses an infrared image sensor that combines an infrared light receiving device (sensor chip) having a two-dimensional array of pixels with a complementary metal oxide semiconductor (CMOS) device forming a read-out circuit (read-out integrated circuit (ROIC)). In this infrared image sensor, the sensor chip is flip-chip connected via indium bumps to the CMOS device. This sensor chip is mounted on a ceramic package together with a Peltier device. A photocurrent generated in each pixel of the sensor chip is output as a voltage via a capacitive trans-impedance amplifier (CTIA) in the read-out circuit, processed by an external field-programmable gate array (FPGA), and then output as a digital signal.
Japanese Unexamined Patent Application Publication No. 2013-41922 describes a problem related to image quality of an infrared image sensor. In this problem, alight receiving device malfunctions due to infrared light entering through through-holes passing through a wiring board. As a solution to this, a light receiving apparatus is proposed, in which the through-holes are filled with resin that transmits visible light and blocks infrared light.